1. Field of the Invention
The present invention relates to a motor and a method of manufacturing the same and, more particularly, to a motor in which a bearing housing is made of resin and, at the same time when the bearing housing is made of resin, a base plate is integrated with the bearing housing a method, such as insert injection, heat fusion, or bonding, thereby being capable of securing the verticality of a bearing and a pivot assembled with the bearing housing and the base plate, reducing the manufacturing cost, improving the efficiency of a manufacturing process, and particularly applicable to a spindle motor for high-speed rotation, and a method of manufacturing the motor.
2. Background of the Related Art
In general, optical disc players, such as an LDP, a CDP, a CD-ROM player, a DVD-ROM player, a DVD player, a BD, and a 3D player, are devices each configured to have a mounting hole, formed to penetrate the center of a disc, to a turntable using a chuck (that is, a clamping unit), while loading the disc on the turntable according to a loading mechanism, and to play information recorded on the disc, clamped to the chuck in one direction, using an optical pickup unit moving in a radius direction thereof while rotating the disc using the driving source of a spindle motor (that is, driving means).
In general, the spindle motor can maintain a rotation characteristic of high accuracy by rotatably supporting a pivot so that a predetermined contact interval is maintained between bearing and a pivot. Accordingly, the spindle motor is being widely used as a hard disc drive (HDD), an optical disc drive (ODD), and means for driving a recording medium requiring high-speed rotation.
It is required the spindle motor requiring high-speed rotation become thin and be reduced in weight in accordance with the development of electronic devices gradually reduced in size. An example of the spindle motor is schematically shown in FIG. 1 (refer to Korean Patent Laid-Open Publication No. 10-2010-0043525)
FIG. 1 is a cross-sectional view of a conventional spindle motor in the axial direction. As shown, the conventional spindle motor is configured to have an outer circumferential face on the bottom end side of a bearing housing 13 inserted into a connection hole formed in a base plate 11 so that external protrusions 13a are coupled through spinning or caulking. A stopper 14 and a cap 15 are connected to an inner circumferential face on the bottom end side of the bearing housing 13 and configured to prevent the pivot 19 from being separated from the inner circumferential face. The cap 15 is connected to the internal protrusion 13b on the bottom end side of the bearing housing 13 through spinning or caulking.
A bearing 17 is fixed within the bearing housing 13. A pivot 19 is supported by and rotatably installed in the bearing 17. A support washer 16 for reducing the rotation resistance of the pivot is disposed within the cap 15 at the bottom of the pivot 19.
Furthermore, a stator 21, including a core 21a and a coil 21b, is fixed to the outer circumferential face of the bearing housing 13. A rotor 23, including a rotor yoke 23a and a magnet 23b, is fixed to the front end portion of the pivot 19.
The top surface of the rotor yoke 23a of the rotor 23 functions as a turntable for fixing and seating a disc D, having data stored therein, thereto and therein. To this end, a rubber ring 12 for preventing the disc D from being slit is disposed on the rotor yoke 23a. A chucking device 18, including a disc chucks 18b and a chuck casing 18a, is provided on the inner side on the top of the rotor yoke 23a and configured to fix the disc D loaded on the turntable.
In the conventional spindle motor, when current is supplied to the coil 21b, a rotary magnetic field is generated, and the disc D mounted on the rotor yoke 23a is rotated by the magnet 23b (that is, the rotor 23) which is rotated by electromagnetic force formed between the coil 21b and the magnet 23b. 
The conventional spindle motor is disadvantageous in that an assembly process is complicated because the connection of the bearing housing 13 and the base plate 11 and the connection of the bearing housing 13 and the cap 15 are performed by a process of spinning or caulking the outside and inside protrusions 13a and 13b. 
Furthermore, in the prior art, when the spinning or caulking process is performed in order to couple and fix the bearing housing 13 and the base plate 11 and the bearing housing 13 and the cap 15, the verticality of the bearing housing 13 to the base plate 11 is frequently deviated. Consequently, when the bearing 17 is pressed to the bearing housing 13, repair is required because the verticality and the run-out problem of the bearing 17 are generated. In this case, if the pivot 19 is assembled with the bearing 17 without repair, there is an advantage in that vibration and noise are generated because the pivot 19 is inclined from the base plate 11.
When the bearing 17 is pressed to the bearing housing 13, the outer diameter portion of the bearing 17 is changed owing to the pressing. Accordingly, the outer diameter portion of the bearing needs to be processed using a sizing process of correcting the change.
Furthermore, if the spinning or caulking process for connecting the cap 15 is bad, there is an advantage in that oil within the bearing 17 leaks through a portion where the bearing housing 13 and the cap 15 come in contact with each other.
In the conventional spindle motor, the bearing housing 13 is made of brass or aluminum material and fabricated by processing or compression processing using a CNC machine. Accordingly, there is an advantage in that the manufacturing cost is high.
In a DVD disc of a half height drive for DVD record, there is a tendency that the disc record speed is increasing so that the DVD disc has the record speed of 16 to 20-speed or higher. In the record speed improvement, a maximum rotation speed of the spindle motor must be 10,500 RPM or higher. If the spindle motor has the high rotational speed, the verticality of the pivot becomes more important in order to prevent vibration and noise.
Furthermore, Korean Patent Laid-Open Publication No. 10-2010-26807 (relating to a spindle motor) proposes the spindle motor capable of preventing the rotation of a bearing holder by forming a burring portion protruding over a plate and forming a connection groove, corresponding to a burring portion, in the bearing holder so that the bearing holder is supported by the connection groove in a circumferential direction, with consideration taken of a problem that the bearing holder is rotated or shaken in relation to the plate by means of external force or rotary power supplied to the bearing holder when the rotor casing and the pivot are rotated.
Meanwhile, Korean Patent Laid-Open Publication No. 10-2007-36350 (relating to a spindle motor for an optical disc drive) proposes a structure in which a shaft holder and a base plate are integrally molded by diecasting or metal-in mold injection and also made of an aluminum alloy or a zinc alloy material having a relatively low specific gravity in order to reduce the weight of the spindle motor for an optical disc driver, thereby reducing the total weight of a mobile communication device.
However, the spindle motor is formed by molding metal material having a relatively low specific gravity in order to reduce weight. A cap for supporting a thrust bearing is separately fabricated and assembled. A spinning process for fixing and connecting the cap and the base plate is required.
Korean Patent Laid-Open Publication No. 10-2007-7517 (relating to a spindle motor) proposes technology in which a bearing housing and a base plate are integrally formed by twice bending the base plate. It is however difficult to secure desired verticality for the bearing housing because it is difficult to mold the base plate in a precise micron order, and axial verticality may be influenced when the stator and the bearing are assembled.